In this investigation, the species of spiked Rare Earth Element La, Gd, Y, Ce and Sm in sediment were def'med as watersoluble, acid extractable and organic/sulphide bound species, the correlation relationship of these species to thebioavailability of algae (Chlorella Vulgaris Beijerinck) were established by linear regression. The results indicated thatthere existed good correlation between the concentrations of REEs in algae and the concentrations of three species insediment, respectively. Among three species in the sediment, the water soluble species had the best correlationrelationship to the bioavailability of algae, this suggested that the release of REEs from the sediment were the most important factor affect the bioavailability of REEs to algae.

A static laboratory aquatic microcosm was conducted to evaluate the distribution of mixed REEs-rare earth dements (lanthanum, cerium, samarium, gadolinium and yttrium) in natural water bodies. Several kinds of species were used. Duckweed represented phytoplankton, daphnia represented crustacean, shellfish represented benthic species and goldfish represented fishes. Samples from water, sediment and each species were analyzed by ICP-AES to determine their REEs contents. It was found that most REEs was adsorbed by sediment and might be redischarged into water, and the bioconcentration order of REEs in the species is duckweed>daphnia>shellfish>goldfish. The results will be useful to evaluate the environmental impact of the wide use of REEs in China.

In this paper, the species of Rare Earth Elements (La, Gd and Y) complexed with organic ligands EDTA (ethylenediamine tetraacetic), NTA (nitrilotriacetic acid) and Cit (citrate) were calculated in the test medium by MINTEQA-A program to calculate aqueous geochemical equilibrium. The influence of the species on the bioconcentration (kinetics and thermodynamics) processes of REEs by algae (Chlorella Vulgarize Beijerinck) were also studied. The results show that the bioconcentration processes of REEs by algae were highly dependent on chemical species. Adding organic ligands which can form RE-Organic species complex led to a great reduction of the REEs bioconcentration in algae. The order of BCFs from high to low is RE3+>RE-Cit>RE-NTA>RE-EDTA complex. The potential mechanism ofbioconcentration may be the coordination reactions of REEs ions with the active sites on algae surface followed by the slow diffusion into the algae cell.

Fulvic acid (FA) was extracted and purified from natural soil and the effects of such FA on the bioaccumulation of rare earth elements (REEs, La3+, Gd3+ and y3+) in wheat seedling were investigated. The results indicated that low concentration of FA (<0.4mg C/1 to root, <0.7mg C/1 to tops (stem and leaves)) could increase the bioaccumulation values of REEs in wheat, but when the concentration of FA was high (>0.4mg C/1 to root, >1.5mg C/1 to tops) the bioaccumulation values were decreased. Kinetic experimental results suggested that bioaccumulation values of REEs in roots for 30 days were correlated with the kinetic linear growth equation, and correlation coefficients were higher than 0.861. The kinetic bioaccumulation pattern of REEs in tops was different from that in root. The bioaccumulation values of REEs in wheat root were much higher than in wheat tops. Variations of glutamic oxaloacetic transaminase (GOT) enzyme activities in wheat root and tops were determined. A good correlation existed between the bioaccumulation values of REEs and GOT enzyme activities, and the correlation coefficients were higher than 0.922. GOT is an im-portant parameter influencing the bioavailability of REEs.